Question

during eruption of volcano ,huge quantity of hot molten substance that comes out of vent

Answer 1

it is called lava
hope it helps

Answer 2

The huge quantity hot molten substance coming out from the vent is called magma, this is a substance that is from the interior of the earth formed as a result of pressure of underlying rocks on the earth's surface. Also this hot molten substance from the interior of the earth may be as a result of heat of underlying material beneath the surface of the earth due to the action of radioactivity,the hot molten substance is called magma